1. Field of the Invention
This invention relates to a process for the production of light colored alkyl or alkenyl polyglucosides.
2. Description of the Related Art
Alkyl oligoglycosides, more particularly alkyl oligoglucosides, are nonionic surfactants which are acquiring increasing significance by virtue of their excellent detergent properties and their high ecotoxicological compatibility. They are normally produced from glucose which is acetalized with fatty alcohols in the presence of acidic catalysts. The catalyst is then neutralized, excess fatty alcohol is removed and the product is bleached.
Basically, acids are used as catalysts for the acetalization. Sulfuric acid, for example, is extremely effective in the condensation, but always leads to very dark-colored products which are difficult or impossible to lighten. In addition, a high content of unwanted secondary products, particularly polyglucose, is observed. In the past, there has been no shortage of proposals for suitable acidic catalysts. For example, p-toluene sulfonic acid and, in particular, anionic surfactants in acidic form, for example long-chain alkylbenzene sulfonic acids, sulfosuccinic acid, alkyl sulfonic acids and sulfuric acid halfesters of fatty alcohols and polyglycol ethers thereof, have been used as catalysts. Unfortunately, all these known processes are attended by the disadvantage that, even after bleaching, the color quality of the resulting alkyl oligoglucosides is not entirely satisfactory. Even in regard to the secondary products, there is a need for substances of reduced polyglucose content. The use of surface-active catalysts leads to intensive foaming during the reaction. Finally, the use of petrochemical catalysts with an aromatic ring structure in alkyl oligoglucosides otherwise based solely on natural raw materials is often undesirable for fundamental reasons.
Accordingly, the cumulative problem addressed by the present invention was to provide an improved process for the production of light-colored alkyl and/or alkenyl oligoglycosides which would be free from the disadvantages mentioned above.